Trade Routes

• Cities
• Population
• Improvements
• Expansions
• Trade Routes

A late-game trading city with the Customs Ministry can produce as much dust as 10 other cities combined.

Trade Routes allow cities to trade with one another, generating Dust and Science.

Mechanics

Generally speaking, a city can create a trade route to another city if both are friendly, and the cities between them are all connected with Right of Way or Cargo Docks improvements. The exact conditions are a bit more complicated:

• Two cities are connected by land if they are in adjacent regions and both have Right of Way improvements. Likewise two cities are connected by sea if both have Cargo Docks and border the same body of water; note that this does not require the Docks to be built adjacent to the same named Oceanic region.

• A city A can create a trade route to another city B if there is a sequence of connected cities (C1, C2, C3, ...) between them, and:
  • None of the cities (A, C1, C2, ..., B) are under siege.
  • All the cities (C1, C2, ..., B) are friendly to A. That is, Ci must either belong to the same empire as A, or the empire owning Ci is at peace or in an alliance, and borders are open between them.
  • There is one exception to the "friendly city" rule: if A is governed by a Roving Clans hero with the skill Black Marketeer, then trade routes from A can pass through, or end at, any connected city regardless of diplomatic and/or border status.
  • If there are multiple paths from A to B, then the only the shortest one will be considered.

For all intents and purposes, a trade route from city A to city B counts as flat / income in A without affecting B in any way. For example:

• A can create a trade route to B, but B may not necessarily create a route back to A.
• The trade route occupies a slot in A without consuming one of B's slots.
• A Caravanserai in A only boosts income for trade routes starting in A and not for trade routes ending or passing through A.
• Likewise an empire only collects income from trade routes starting from its own cities, not from other empires' incoming trade routes.

A city may create one trade route by default, with additional technologies and city improvements increasing this limit. If a city has multiple possible choices for trade routes, it will automatically select those with the highest / income.

The status of all trade routes in the empire is displayed in the Empire Management Screen (default keybind F1).

Yield Formula

A trade route's base Dust and Science income is determined by the distance between the cities and the population of the destination city. This base value is then modified by a number of other effects, listed in the section below.

BaseIncome = 1 + 0.6 × DestinationPopulation + 0.18 × TradeRouteDistance
 Yield = BaseIncome × (1 + TradeRouteBonus) × (1 + TradeRouteDustBonus)
 Yield = BaseIncome × (1 + TradeRouteBonus) × (1 + TradeRouteScienceBonus)

Notes

1. DestinationPopulation does not include bonus population (from pacified villages, the Chapel of Auriga, and so on).
2. TradeRouteDistance follows the path of the road, or coast in the case of an ocean route. The exact path can be seen by selecting the city, then zooming out slightly so the map is visible.
3. The Grassilk booster is applied after the above formula: its bonus is not added to TradeRouteDustBonus, but rather it simply doubles the dust income from trade routes after everything else has been computed. This means that it is extremely effective at increasing dust income from trade routes.
4. Trade routes' yields are considered part of the city's normal / income, so they are modified by city- or empire-wide bonuses like the Empire Mint or Museum of Auriga.

Trade Route Modifiers

Name	Type	Unlocked	Effect
Right of Way	City Improvement	Era II	Enables trade routes. Connects cities by land.
Cargo Docks	City Improvement	Era III ( Era II for Morgawr)	Enables trade routes. Connects cities by sea.
Palace	City Improvement	Empire Capital	+1 Trade Routes max on city
Negotiation Tactics	City Improvement	Era II Legendary Deed	+50% Trade Route Bonus on City Trade Routes.
Caravanserai	City Improvement	Era III	+1 Trade Routes max on city +50% Dust on city trade routes
Scientific Envoy	City Improvement	Era V (Not Forgotten)	+1 Trade Routes max on city +50% Science on city trade routes
Surreptitious Research	City Improvement	Era V (Only Forgotten)	+1 Trade Routes max on city +50% Dust on city trade routes
Customs Ministry	Unique Building	Era V	+7 Trade Routes max on city
Traders' Tents	City Improvement	Roving Clans Faction Quest Chapter 4	+50% Dust on city trade routes
Well of Dust	City Improvement	Roving Clans Faction Quest Chapter 7	+2 Trade Routes max on city
Safe Passage	Hero Skill	Roving Clans Heroes	3 levels. +25%/+25%/+50% Trade Route Bonus in governed city.
Fast Trader	Hero Skill	Roving Clans Heroes	3 levels. +50%/+50%/+100% Dust on trade routes in governed city.
Black Marketeer	Hero Skill	Roving Clans Heroes	Allows governed city to create trade routes with factions at war or cold war.
Mechanical Exhibitionist	Hero Skill	/ Vaulters/Mezari Heroes	3 levels. +50%/+50%/+100% Science on trade routes in governed city.
Commercial Agreement	Diplomatic Action	Peace/Alliance	Increases the Dust gained from trade routes with the targeted empire (+1% each turn, up to 20%).
Research Agreement	Diplomatic Action	Peace/Alliance	Increases the Science gained from trade routes with the targeted empire (+1% each turn, up to 20%).
Inflation	Diplomatic Action	Roving Clans Faction Quest Chapter 8	-50% to targeted empire's trade route / income.
Improved Trade Routes	Empire Plan Economy and Population level 3	Era III	+50% bonus to trade routes
Grassilk Booster	Luxury Resource booster	Era III	+100% Dust on trade routes
Cargo Nexus	Unique Facility	Era III	+5% bonus to trade routes, with +1% additional bonus per Fortress controlled by the empire.

Secondary Trade Routes

When a trade route passes through multiple cities, all the cities between the origin and destination receive a small amount of bonus income, called a Secondary Trade Route. This income is a small proportion of the base income of the primary trade route and does not seem to interact with trade route modifiers. And, while a city may be limited on how many primary trade routes it can create, it can have an unlimited amount of secondary trade routes passing through it.

Strategy

Starting from Era II, trade routes become a critical source of Dust and Science for almost every faction, with the income vastly exceeding earned from city tiles and/or Population. Optimising trade routes is a great way to drive empire development as well as accelerate an economic victory.

The main reason why trade routes have such a high payoff is due to the way its multipliers stack. The following are all multiplied together:

• TradeRouteBonus (1.25x in the early game, 2.5x to 3x later)
• TradeRouteDustBonus (1x in the early game, 3x to +3.5x later)
• Grassilk booster (2x)
• All other bonuses to city production. (1.15x in the early game, 2x to 3x later)

This is also multiplied by number of trade routes and trade route distance, which increases as an empire expands or gains more trading partners through Diplomacy. The general trend is that each new Research, Skill, City Improvement, Empire Plan bonus, etc... unlocked or built leads to a significant increase in income, making trade the fastest scaling FIDSI source in the game. By comparison, other sources of / rely on tile yields and Population, and do not have nearly as many multiplicative bonuses.

Diplomacy

The current empire can create trade routes to the Allayi that pass through the Kapaku, but because the Allayi and Kapaku are not at peace themselves, the Allayi cannot create trade routes back.

Expanding trade aggressively through diplomacy benefits the player disproportionately compared to AI opponents. This is for several reasons:

• Higher difficulty AI cities are not only farther away, but also tend to have much higher population.
• Trade routes are one-directional, and so are their benefits. Suppose the player A is at peace with empires B (nearby) and C (far away). Then A can create highly profitable trade routes to C through B; but unless B and C are also at peace with each other, C cannot create trade routes back to A.

So trade routes can serve as a catch-up mechanic that allows a weaker faction to take advantage of the development of stronger ones.

Roving Clans Heroes and the Customs Ministry

Roving Clans heroes greatly buff trade routes in a governed city. Most notable is the skill Black Marketeer, which allows a city to form trade routes to any city regardless of diplomatic status. This has a similar effect to the diplomacy strategy above (lengthening trade routes and multiplying trade income in a city by several times), except it is resilient to diplomatic shifts, such as a sudden (cold) war declaration.

In the mid game, it is recommended to recruit at least one Roving Clans governor in order to reach Black Marketeer quickly. At this point, the governor can be placed in a faction's capital, whose Palace building provides an extra trade route.

Later the Era V Customs Ministry adds +7 trade routes to a city. So in the mid- to late-game it becomes highly profitable to settle or conquer a city at the edge of the map in order to maximise trade route distance. With 9-10 trade routes heavily boosted by the National Craftworks, Dust multiplier buildings, and a Roving Clans governor, this trading city can easily generate more than the rest of the empire, and this is one of the most expedient ways to win an economic victory.